Obviously this is a good deal if Fidelity is the right investment for you. In other words, if by chance you were already about to choose a Fidelity fund because you felt it was the best fund for your needs, these are free miles.

But like any financial deal with miles involved - whether it's banking, mortgage, brokerage, or credit - there is an opportunity cost involved. Sometimes a BIG one (particularly in the case of mortgages!). Make sure you don't overrate the value of 25,000 United miles and let that guide you into making a suboptimal investment.

(Nothing against Fidelity Investments: I have held several of their funds for many years.)